1. Field of the Invention
This invention relates generally to television receivers and more particularly to giant screen, projection type television receivers.
2. Description of the Prior Art
Projection, or giant screen, television has been around for many years. A reason behind the interest in giant screen television is that many people feel that a conventional television picture, usually measuring no more than 25 inches on the diagonal, is simply not large enough for truly enjoyable viewing, and would prefer a projection television system having a viewing screen size ranging upwardly from 40 inches on the diagonal.
There are at least three systems in current use which project a large television image upon a screen. The first, and technologically least complicated, system utilizes a lens system to magnify the image produced by a standard television C.R.T. and to project the magnified image upon a viewing screen. Examples of such systems are found in the disclosures of E. Muntz in U.S. Pat. Nos. 3,943,282 and 4,058,838 and of A. Cammilleri in U.S. Pat. No. 4,074,322. Projection televisions of this type have the advantage of being considerably less expensive than other types of projection television systems.
A second type of projection television system utilizes three separate nonstandard C.R.T.'s to produce a relatively bright image upon a viewing screen. Systems such as these have a red tube, a green tube and a blue tube to project separate red, green and blue images which merge together into a single color image at the viewing screen.
While three-tube systems produce a brighter image than the lens and standard C.R.T. systems, they are also considerably more expensive. Furthermore, three-tube systems usually require that the unit housing the three nonstandard C.R.T.'s be separated from the viewing screen by a considerable number of feet. This may be undesirable for some potential customers since a large screen and separate projection unit can undesirably dominate a room's decor. Furthermore, a person walking between the projection unit and the screen can partially block the projected image and thus interfere with the viewing enjoyment of others. Lastly, most all two-piece systems require that wires be run between the projection unit and the screen with inconvenient, unattractive and sometimes dangerous results.
Finally, there is an oil-film type of television projection system which utilizes a thin, translucent film of oil capable of creating a television picture image. Extremely high intensity colored lights are directed through the oil-films to produce a superbright television image upon a viewing screen. Oil-film projection televisions are extremely expensive, often causing many tens of thousands of dollars, and are usually reserved for large scale applications such as within football stadiums or large municipal auditoriums.
A major problem with many projection television systems found in the prior art is that they are usually large, bulky units requiring many feet of floor and wall space. The large size of the systems and the constantly exposed viewing screen further tend to undesirably dominate the decor of a room.
Another problem with projection television systems found in the prior art is that the projection screen, which is highly sensitive to dust, smoke and hand oils, is always exposed to damage. Over a period of time, such hazardous exposure would necessitate frequent cleaning and could necessitate the expensive replacement of the viewing screen.
A problem with the low-cost lens and standard C.R.T. systems is that the picture image on the C.R.T. must often be inverted and/or reversed so that a correctly oriented image will appear on the viewing screen. This inversion and/or reversal is usually accomplished by permanently switching leads on the C.R.T.'s yoke. Due to this modification, the television receiver cannot readily be used independently of the projection television system. Another problem with these inexpensive systems is that they typically can only accommodate one or two sizes of televisions due to various physical and optical restraints.